Abstract: This design idea describes a simple circuit to generate a programmable negative control voltage. It takes the output of a single supply digital-to-analog converter (DAC) and produces a variable negative voltage. The DAC output from 0V to +2.5V is converted to 0V to -5V at the output. Early digital-to-analog converters (DACs) were designed with standard R-2R ladders, and produced a negative output voltage. These early DACs (such as the MX7837/MX7847 and MAX523) require both a positive and a negative supply rail to accommodate their negative output. With the transition to single-supply integrated circuits, however, many modern DACs now operate with a single supply rail and an inverted R-2R ladder. The inverted R-2R ladder produces a positive output voltage. Despite the popularity of single-supply ICs, some applications still require a negative control voltage. One solution for this purpose is a modern, inverted R-2R ladder DAC and op amp (Figure 1). When compared with older DACs containing standard R-2R ladders, this approach offers lower supply voltages, higher speed, and smaller packages. Figure 1. This compact circuit enables microcontroller IC2 to generate a variable negative voltage. The DAC (IC3), operating with a 2.5V applied reference voltage from IC1 and driven by microcontroller IC2, produces an output swing from 0V to 2.5V. Op amp IC4 inverts and amplifies this output to produce a 0V to -5V output. For test purposes, a software routine enables the microcontroller to generate a 0V to -5V triangle-wave output. Please note that the output impedance of the DAC (IC3) is 6.25kΩ ±20%. To eliminate system gain errors that are caused by the DAC's output impedance, buffer the DAC output before the IC4 inverting stage. A similar version of this article appeared in the December 6, 2001 issue of EDN magazine. 相关型号   APP 1074: May 24, 2002 MAX4162 SOT23封装、微功耗、单电源、满摆幅输入/输出运算放大器 完整的数据资料 (PDF, 304kB) 免费样品 MAX541 +5V、串行输入、电压输出16位DAC 完整的数据资料 (PDF, 248kB) 免费样品 MAX542 +5V、串行输入、电压输出16位DAC 完整的数据资料 (PDF, 248kB) 免费样品 MAX837 4引脚、微功耗电压监视器 完整的数据资料 (PDF, 108kB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (29kB)  AN1074, AN 1074, APP1074, Appnote1074, Appnote 1074